1. Field of the Invention
The present invention generally relates to accelerator tubes used in hydraulic food cutters, and more particularly relates to improved flexible accelerator tubes.
2. Background Information
Hydraulic food cutting apparatus have been known and used commercially for over thirty years. Their general principles of operation are well known. Food pieces to be cut, typically potatoes, are dropped into a feed tank containing water. The water, with the entrained potatoes, is then pumped into a pipe and into the front half of a venturi where the potatoes are accelerated to velocities of approximately forty to sixty feet per second. At the narrowest point of the venturi, a fixed array of cutting blades is positioned, and as the food product impinges upon the blade it is cut into a plurality of smaller pieces, for example french fry pieces cut from whole potatoes. The cut food pieces then enter the second half of the venturi where they are decelerated and deposited upon a chain conveyor of some sort wherein the water passes through and the cut food pieces are separated from the water. The water is then recycled back to the feed tank for further use. The cut food pieces are then conveyed on for further processing as appropriate.
While the concept is simple, its execution in practice is far more difficult. The commercial value of the cut food pieces is dependent upon the quality of the cuts. Broken or irregular cut food pieces have less commercial value and as a result continuous work has been done over the years to improve the quality of the cut food pieces coming out of a hydraulic cutter.
While there are a wide variety of food products that are cut using hydraulic food cutters, the predominant use is for cutting potatoes, and as such will be used as an example of some of the problems encountered when attempting to cut food product into pieces. However, it should be distinctly understood that the use of potatoes is for illustrative purposes only, and by no means is intended to limit the scope of the present invention. Other products that can and are cut with hydraulic food cutters include other vegetables, such as onions, carrots, beets, and even mushrooms, as well as fruits.
The cellular structure of a potato is relatively rigid and a lot of starch is present. When the potato impinges upon the cutting blade within the fixed array, the cutting forces tear apart cell structures, and considerable frictional forces are encountered. Given the fact that the hydrodynamic forces within the cutter assembly are very difficult to accurately model, new designs are usually the result of trial and error testing. A poor design can leave food products and cut pieces tumbling and colliding with each other or walls of the hydraulic food cutter causing numerous broken pieces to be created. Additionally, it is believed that the frictional forces encountered by the potato and the partially formed cut food pieces induce shear forces in the cut food pieces resulting in a condition known as feathering wherein the cut potato pieces, particularly french fries, may come out of the hydraulic food cutter with a plurality of smaller feather cuts generally oriented forty-five degrees to one or more corners of the french fry. Also, the uncut food product itself may not be perfectly aligned with the array of cutters, thus resulting in misaligned cut food pieces.
A number of steps have been taken to improve the quality of the cuts. One of these is that the potatoes are preheated and/or the feed water is preheated. Preheating has been found to reduce the number of misaligned cuts, broken pieces, and feather cuts. Another improvement is the introduction of the accelerator tube in the converging portion of the venturi immediately in front of the fixed array of cutter blades. These accelerator tubes are frustoconical in shape, and come in a variety of sizes and interior diameters, which are sized for the particular size of food product being cut. Accelerator tubes serve the function of accelerating the food product prior to impingement upon the fixed array of cutter blades and also to align and sequence the food product to minimize tumbling.
Typical prior art accelerator tubes are made of rigid natural rubber and are held in place at a discharge end by means of pneumatically controlled alignment shoes to minimize the wobble of the discharge end of the accelerator tube as the uncut food product is ejected out the discharge end and into the cutter blades. A typical prior art accelerator tube assembly can be seen in U.S. Pat. No. 5,568,755. While the use of a prior art accelerator tube improves the quality of the cut food pieces, the prior art accelerator tubes have by no means provided a complete and satisfactory solution to quality problems. One of the primary problems with these prior art accelerator tubes is that the uncut food products are not of uniform size, and one size accelerator tube does not fit all. If an oversized uncut food product is propelled through the accelerator tube, it will expand the cylindrical wall of the accelerator tube at the discharge end, and thereby force the accelerator tube to engage the guide arms. This produces a wobble in the accelerator tube and the uncut food product being ejected from its discharge end, which can seriously degrade the quality of the cut food pieces. Another problem with the existing prior art accelerator tubes is that they are relatively rigid and inflexible, and the uncut food product that is too large for the accelerator tube may not be able to pass through it, but rather jam inside it. At cutting rates of 30,000–60,000 pounds of potatoes per hour, it does not take but a few seconds for a jammed potato in the discharge end of an accelerator tube to cause a plug up of mashed and damaged potatoes in the feed line that may take hours to remove and clean up.
Another problem with the prior art hydraulic food cutters and accelerator tubes is that the accelerator tubes have to be fixedly attached in the feed line, which is usually accomplished by bolting a flange of the accelerator tube to a fixed structure on the hydraulic food cutter. The same is true for the cutter head assembly containing the arrays of fixed blades. It is a common practice in the potato processing industry to replace the cutter blade assembly for purposes of replacing or sharpening the blades after six to eight hours of use. It is also common practice in the prior art to periodically change and/or replace accelerator tubes as they wear or need to accommodate various sizes of uncut food product being processed. Both of these operations, in the prior art, are time consuming and therefore expensive in terms of production downtimes.
Accordingly, what is needed is a new, improved accelerator tube that further reduces induced wobble or tumbling in the uncut food pieces, but is flexible enough to allow the passage of oversized uncut food pieces, thus to minimize plugging problems. What is also needed is a means for replacing the accelerator tube within the hydraulic food cutter with minimal downtime for the cutter assembly.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.